Update 2/10/25:
Very interesting development. It seems that nyctinasty might be an exclusive trait in micro-dwarfs.
Here's an image of a seedling not expressing nyctinasty(#7) and one that is(#8). The phenotype is quite distinct.


In addition, the segregation ratios are very strange. Dwarf(d) might not be the only gene responsible for causing the plant to express no nyctinasty. If we include the first F2 trials, only 4 out of 33 individuals so far exhibit no nyctinasty. This is much less than the number of actual plants that should have exhibited the dwarf(d) gene. There should have been around 8 plants that are at least dwarf, but it seems that around half of those individuals close their cotyledons at night instead of keeping them open.

This leads to the hypothesis that multiple genes may be triggering no nyctinasty, as well as causing a shorter seedling height. The dwarf gene may be one of the genes causing this, since all F2s so far in the previous generation are indeed dwarf.

This other gene or other sets of genes are definitely not recessive, as that would only give 2 out of 33 to exhibit that phenotype instead of 4. But if it were dominant, 24-25 out of 33 should have exhibited no nyctinasty.

So how do we solve this interesting problem? My hypothesis would likely be epistasis, or a gene that is dependent on the presence or absence of another gene for expression. So in this situation, let's say there are 2 genes: Dwarf and No-Nyctinasty.

Dwarf can be expressed regardless of nyctinasty. However, if we assume No-Nyctinasty can be expressed ONLY when the plant is homozygous recessive for the dwarf gene, then the ratios change.

What happens when no nyctinasty is recessive, but requires being homozygous for the dwarf gene?
Individuals: 32(an even number for convenience)
Percent chance dwarf: 25%
Percent chance homozygous for No-nyctinasty: 25%
Percent chance of being dwarf and has No-nyctinasty: 6.25% or 2 out of 32 individuals.

What happens when No-nyctinasty is dominant, but requires being homozygous for the dwarf gene?
Percent chance dwarf: 25%
Percent chance being heterozygous or homozygous for No-nyctinasty: 75%
Percent chance dwarf and expresses No-nyctinasty: 25% x 75% = 18.75% = 6 out of 32 individuals. This might be closer to the 4 in 33 possibility.

Therefore, I suspect that there is a micro-dwarf gene that is only expressed as a dominant trait when the plant is homozygous for the dwarf gene. Perhaps it's another mutation that causes another downstream hormone deficiency. I currently have seedling #16 germinating in the humidity chamber, and I suspect that it's possible it might be another no-nyctinasty individual. I am very curious to see what more F2 seedlings will yield.

Update 2/11/25:


Seedling #16 has sprouted. I have cropped and size corrected the seedling as reference compared to the other seedlings. #16 also has the shortest root size out of the lot and the widest stem diameter, which makes me wonder if it has more micro genes. I have planted #16 in position 1. It has been around 2 days since I have planted the seedlings, and now none of the seedlings planted on February 9th display nyctinasty. It seems that this phenotype is quite short lived.

If my hypothesis is correct, following the phenotypes/behaviors at the cotyledon stage of the seedlings might be the key to early selection. Smaller root mass in my F3 trial might possibly indicate leaflet reduction, but that is speculation due to a sample size of 1 instance. Seedling #16 will help me determine if that is true.

Based off my logs, it seems that the 1-3-5 leaflet pattern is an incompletely dominant trait that can pop up in individuals that have a 3-5-5 leaflet pattern(An intermediate of the 3-5-7 and the 1-3-5 pattern). I wonder if this is related to Nyctinasty. Based off of this, I may need to grow out at least 64 total seedlings to be homozygous for dwarf, leaflet reduction, and early termination(likely a variation of self pruning/determinate). However, 3 out of the 64 will likely have an extremely compact size with partial leaflet reduction.

It's hard to affirm these observations of no-nyctinasty as valid indications of genetics without a lot more data.
I know you are working small space and basically impossible to grow and observe the growth habit of all the seedlings. Maybe recruit some group of micro growers and micro breeders here to contribute observations of their seedlings as well.
I'm not growing any micros (well I don't plan it at this point) but I will certainly observe my seedlings closely for the signs of no-nyctinasty, and report back if I find any among non micros.

bower wrote: ↑Wed Feb 12, 2025 7:44 am It's hard to affirm these observations of no-nyctinasty as valid indications of genetics without a lot more data.

I agree, I do have more plans on growing out more F2 seedlings to see if there's a consistency in the trait with growth habit. As far as genetics are concerned, No-Nyctinasty seems to be a conserved trait in the micro parent as well as several other varieties. So much so that I found it highly irregular for cotyledons to close at night when I grew my first normal indeterminate tomatoes. This experiment is mainly a test to record down segregation and aggressively selecting the parental micro traits.

In terms of recruiting others to perform grow outs, I am very particular of the selection process, logging about 30 phenotypes per fully grown individual, and constantly observing for anything new to record down. That might be a bit too exhausting and unreasonable for any normal person to do. In addition, the flavors and sweetness of the F2 and F3s are not up to par.

However, I might be interested in releasing the backcrossed seeds if the flavor is drastically improved and if I find a way to refine the micro selection process. This way, we could truly test replicability as well as guaranteeing good flavor.

Not sure if I missed something - is the non-closing at night pheno standard for all micros?
Is a short-lived period of closing at night then an indication of partial set of micro genes, only at the earliest stage.
Sorry, I'm a little brain dead from shoveling snow in the freezing cold. Maybe catch up on this later..

Sorry about not being clear.

I can't say that non-closing at night is the absolute standard, just for all the varieties that I grew (Micro-Tina, Orange Hat, Jochalos, and Vilma).

1) No-nyctinasty: Do not close cotyledons at night at all.
2) Nyctinasty seedlings: Close their cotyledons for the first 2 days of growth, then cease to close their leaves at night after 2 days or when the first leaf is grown.

When I mean short lived, I was mainly talking about the seedlings that do display nyctinasty, as they only close their leaves at night for a set period of growth. This makes differentiating this phenotype quite time-sensitive.

Closing at night is something I've seen in ordinary tomato seedlings well past the cotyledon stage iirc. Young seedlings.
I have noticed it when turning off the lights at night, that they had already 'gone to sleep'. Mine are in a window though so they had some daylight and then night, while lights continued on.
Are your lights on a timer? And, have you determined what length of 'day' the seedlings have before displaying the cot closing (or not). Just curious about the phenomenon generally, which I have seen but not paid attention to as a trait.

I appreciate the attention to detail which you're applying to find those early phenos of the micro.

bower wrote: ↑Wed Feb 12, 2025 2:27 pm Closing at night is something I've seen in ordinary tomato seedlings well past the cotyledon stage iirc. Young seedlings.
I have noticed it when turning off the lights at night, that they had already 'gone to sleep'. Mine are in a window though so they had some daylight and then night, while lights continued on.
Are your lights on a timer? And, have you determined what length of 'day' the seedlings have before displaying the cot closing (or not). Just curious about the phenomenon generally, which I have seen but not paid attention to as a trait.

We can assume zero outdoor sunlight is in the equation. The lights are on a timer that is around 16 hours from 7:30am-9:30pm. So within the 2 days of being planted, they had a total of 32 hours of light that's around 40,000 lux in intensity.

Oh, that's rather intriguing. Based off my photo meta-data, the cotyledons begin closing at around 6:30pm and fully close at around 8:00pm, 1-2 hours before the lights even turn off.

I am germinating some Rosella Cherry seedlings to re-observe to see when the cotyledons stop closing at night.

Update 2/15/25:


Seedling #4: Nyctinastic, Normal leaf, meristem terminated after 2 leaves.
Seedling #7: Non-nyctinastic, Rugose leaf, meristem terminated after 2 leaves.
Seedling #8: Nyctinastic, Normal leaf, meristem seems to be growing like normal.
Seedling #12: Non-nyctinastic, Rugose leaf, meristem terminated after 3 leaves. Axillary shoot seems to be growing between the last 2 leaves. Right cotyledon is bifurcated.
Seedling #13: Nyctinastic, Normal leaf, meristem terminated after 2 leaves. Right cotyledon is shortened.
Seedling #16: Nyctinastic, leaves and stem structure too early to tell.

Very strange phenotype arrangement yet again. It looks like the possible gene responsible for the termination of the vegetative cycle of the main stem is independent from Nyctinasty and the dwarf gene. The rate of occurrence seems too high for early meristem termination to be merely coincidence/blindness at this point.

Perhaps my next batch of seedlings should be grown out to at least 2 leaves to monitor a meristem termination gene. More seedlings need to be grown for reference purposes.

Update 2/16/25:


Rosella Cherry seedlings have sprouted. Root length is considerably longer than the F2s except for seedling #3